Hydromechanical braking system for road vehicles



Feb. 23, 1954 A. w. ELLCOCK HYDROMECHANICAL BRAKING SYSTEM FOR ROAD VEHICLES 3 Sheets-Sheet 1 Filed Aug. 15, 1950 INVENTOR ARTHUR w ELLCOCK ATTORNEY Feb. 23, 1954 A. w. ELLcocK HYDROMECHANICAL BRAKING SYSTEM FOR ROAD VEHICLES 3 Sheets-Sheet 2 Filed Aug. 15, 1950 l I 25's....

. INVEILITOR ARTHUR w. ELLCOCK AT TORNEY 1954 A. w. ELLCOCK HYDROMECHANICAL BRAKING SYSTEM FOR ROAD VEHICLES 5 SheetsSheet 5 Filed Aug. 15, 1950 n all m GE lNv'ENTOR ARTHUR w ELLCOCK ATTORNEY Patented Feb. 23, 1954 HYDROMECHANICAL BRAKING SYSTEM FOR ROAD VEHICLES Arthur W. Ellcock, Barnt Green, near Birmingham, England, assignor to The Austin Motor Company Limited, Northfield, Birmingham,

England Application August 15, 1950, Serial No. 179,507

2 Claims.

The invention relates to hydro-mechanical braking systems for road vehicles, that is to say systems in which the brakes of one pair of road wheels, usually the front wheels, are operated hydraulically and those of the other or rear pair are operated mechanically.

In a known braking system of this kind in which the front brakes are operated hydraulically and the rear brakes mechanically, actuation of the foot pedal has the effect of applying both sets of brakes simultaneously through the medium of a compensating lever, and the actuation of the hand brake has effected full and positive application of the rear brakes and light application of the front brakes.

In a hydro-mechanical braking system according to the present invention, actuation of one brake control, preferably the foot brake, has the effect of positively applying the hydraulic brakes and of applying the mechanical brakes through resilient means so as to afford a progressively increasing proportion of hydraulic braking to mechanical braking with increasing brake applying pressure on said control.

According to a further feature of the invention, actuation of one brake control, preferably the hand brake, has the effect of positively applying the mechanical brakes, as before, and, through secondary resilient means, of lightly applying the hydraulic brakes, irrespective of the degree of application of the mechanical brakes. The secondary means operate to maintain a substantially constant light fluid pressure in the hydraulic system and consequent constant light braking pressure on the hydraulic brakes, when the hand brake is applied, irrespective of variations in the volume of the liquid due to temperature changes.

The invention will now be described with reference to the embodiment shown, by way of example, in the accompanying drawings, in which:

Fig. l is a side elevation, partly in section, of the hydro-mechanical braking system, the parts being in their normal or inoperative positions.

Fig. 2 is a similar view to Fig. 1 but showing the foot brake applied.

Fig. 3 is a similar view to Fig. 2 but showing the hand brake applied.

Referring to the drawings, in which like parts are given the same reference numbers in all the figures, I is the chassis frame of the vehicle, 2 is the floor of the vehicle body, 3 is the toe-board, and 4 is part of the scuttle or dash structure of the vehicle body. The hand brake control 5 is of the pull-up pistol grip type which, through a cable 6, operates a double-ended lever I mounted by a pivot 8 in a bearing 9 on the chassis 1, while the foot brake control is a pedal lever I0 mounted to pivot on a shaft l l fixed to the chassis I.

The pivotal boss of the pedal lever l0 has a radially extending and laterally offset nose portion I2 afiording an abutment for co-operation with an adjustable screw abutment l3 on a forwardly extending portion of the lower arm of a two-armed lever 14 which is also pivoted on the shaft ll immediately alongside the pedallever Hi. The lower arm of this lever l 4 is directly connected to the ram of the usual hydraulic master braking cylinder I5 which is maintained replete with working fluid by way of a supply pipe It from a reservoir (not shown) and has its pressure outlet I! connected by a pressure pipe line 38 to the front wheel brake actuating cylinders 53, 54, of front wheel brakes 63, 64 or front wheels 55, 6B in the usual manner. The pedal lever I!) is held up by a tension spring [9 anchored to the chassis, and normally, as seen in Fig. 1, there is a small clearance between the abutments l2 and I3 to allow a certain amount of free movement for the pedal lever l0 before it positively actuates the lever M to apply the hydraulic brakes associated with the front Wheels.

The upper arm of the lever M is bifurcated and straddles a movable element or pull rod 20 which slides through a diametrical hole in a transverse pin 2| which is turnable in bearing eyes 22 afforded by the bifurcations of said lever I l. Two collars 23, 24, slidably mounted on the pull rod 20 and on opposite sides of the transverse pin 2! are operated upon by opposed helical compression springs 25, 26 which are sleeved over the pull rod 20 and at their remote ends bear against fixed abutments 21, 28 respectively, which latter abutments are fixed on the rod 20 which is loaded real-wardly by a tension spring 29 anchored to the chassis I, while the forward abutment member 28 has a pin-and-slot lost motion connection 30 with a forked member 3| on a rod 32 connected to the shorter arm of the hand-brake lever l, which rod 32 is also loaded rearwardly by a spring 33 anchored to the chassis I. The rear end of the rod 20 is connected through a turnbuckle 34 to a lever 35 which depends freely from a fixed pivot 36 on the chassis l and operates, through a rod 31 and lever arm 38, a double-ended lever 39 which turns about a vertical axis 40 and has its ends connected by laterally extending actuating rods 4|, 42 to the mechanical brakes 5|, 52 of the left and right hand rear wheels BI and 62 respectively. In the drawings the parts 31, 38, 39,

lighter spring 25 acting upon the pin 2! through the collar 23.

When the hydraulic brakes are positively ap' plied by depressing the pedal ID the forward movement of the upper end of the lever I 4, carrying the transverse pin 2|, is transmitted by the stronger spring 26 and the abutment member 28 to the rod so as to apply the mechanical rear brakes and as the brake-applying pressure on the pedal I8 is increased the spring 26 operates to aflord a progressively increasing proportion of hydraulic braking tornechanical braking (see Fig. 2). Thus under normal braking conditions the foot brake provides the greater braking effort at the front wheels and also for automatic increase in front wheelbraking in proportion to back wheel braking as forward weight transfer ence takes place with increasing deceleration.

When the hand brake is put on the rear brakes are directly and positively applied through the rod-20 and the associated mechanical linkage once the lost motion has been taken up. The forward movement of the rod 29, with its abutments 21, 28, relieves the spring 26 and causes the compression of the spring to be so in creased as to push the pin Z-l forwardly somewhat to create and maintain a constant light applicationof the hydraulic brakes irrespective of the degree of application of the mechanical brakes and irrespective of variations in volume of the brake fluid due to temperature changes.

Having fully described my invention, what I claim and desire to secure by Letters Patent is:

,1. A hydro-mechanical braking system for a road vehicle having front and rear pairs of Wheels, comprising in combination hydraulically applied brakes for a front pair of road Wheels, a hydraulic master cylinder for operating said brakes and having its ram actuated-by a lever, a pedal lever adapted to cooperate with said actuating lever to apply the hydraulic brakes chanical brakes so as to aiford a progressively positively, mechanically applied brakes for a rear pair of road wheels, a pull rod operated by a hand control for positively applying the mechanical brakes, a sliding pivotal connection between said actuating lever and said pull rod, and opposed springs on said pull rod and operating between said sliding pivotal connection and abutments on said pull rod, one spring being stronger than the other and operating, when the hydraulic brakes are positively applied, to apply the meincreasing proportion of hydraulic braking to mechanical braking with increasing brake-applying pressure on the pedal lever, the weaker spring, when the mechanical brakes are positively applied, operating to apply the hydraulic brakes lightly and maintain such light application irrespective of the degree of application of the mechanical brakes.

2. A braking system comprising a vehicle having front and rear wheels, hydraulically actuated brakes for some of said wheels and mechanically actuated brakes for the other of saidv wheels, an operating lever on said vehicle, a master cylinder actuatable from said lever having communica tion with said hydraulically actuated brakes, a rod slidably engaging said lever connected to said mechanical brakes for actuating said mechanical brakes, abutments on said rod spaced from said lever on opposite sides thereof, and springs between said abutments and said lever whereby when said lever is manually operated said hydraulic brakesare positively applied and said mechanical brakes are resiliently applied through one of said springs, and a manual control having a lost motion connection with said rod for applying said mechanical brakes posi tively and resiliently applying said hydraulic brakes through the other of said springs.

ARTHUR W. ELLCOCK.

References Cited in the file of this patent UNITED STATES PATENTS 

